1. Field of Invention
The present invention relates to a pin setting circuit. More particularly, the present invention relates to the pin setting circuit for setting a clock setting pin of a chip.
2. Description of Related Art
No matter what function the individual chip performs, most chips need to be driven by the clock signal. In high-frequency chips having the phase-locked loop, the frequency of the clock signal is increased to the radio frequency. In the digital signal processing chip or the micro-control chip, the clock signals are used to process each stage of computing. Other sequential circuits require the clock signal as a reference signal.
In general, there are two ways the chip can generate a reference clock, one way is to use external crystal oscillator modules, such as Colpitts Crystal oscillator circuit; another way is to add capacitors or the parallel module crystal to the reference circuit of the chip set, such as quartz crystal.
No matter how to generate clock signals, the clock setting pin of the chip needs to be set according to the required clock frequency in order to make the chip identify the operating frequency and work correctly. For example, the clock setting pin needs to be set to logic 1 or logic 0 such that the chip can work at the correct frequency.
However, the clock setting pin may not be set correctly if the clock signal works with various frequencies, and the chip can not function properly as a result. Hence there is a need for a clock pin setting circuit which can set the clock setting pin of the chip according to the clock signal frequency in order to make the chip work correctly.